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REGUB Medicine: Pit & Adrenal Disease (i) (Acromegaly (abnormalities…
REGUB Medicine: Pit & Adrenal Disease (i)
Intro
post pit: oxytocin, ADH
ant pit: TSH, ACTH, FSH, LH, GH, PRL, endorphines (act on pain Rs in brain)
pit diseases have distinct phenotypes
bitemporal hemianopia due to optic chiasm compression by large pit tumour
hypogonadism (low testosterone: reduced libido, ED, reduced body hair (esp axillary), small soft testes
PRL only low in severe pit failure
pit tumours can be an incidental find (e.g. CT of sinuses)
Assessment of pit function
insulin tolerance test
tests GH, ACTH + cortisol production
respond to hypoglyc, hence should be suppressed by glucose load
requires adequate hypoglyc (<2.2)
IV insulin 0.15 u/kg
normal GH>5ng/ml, cortisol>500nM
CI: seizures, IHD
Short synacthen test (SST)
IM synacthen (synthetic ACTH)
check cortisol @ baseline + @ 30 mins
normal response = cortisol > 500nM @ 30mins - if it doesn't rise then adrenal insufficiency
basically no CIs
Thyroid axis
fT4, TSH
secondary hypothyroidism
low fT4 + inappropriately low (which could still be normal) TSH - should rise in response to low T4 (central)
gonadal axis
check testosterone in morning
estradiol
FSH/LH
deficiency in men: low testosterone, low/normal FSH/LH (central)
deficiency in women: low estradiol with low/normal FSH/LH, amenorrhoea/oligorrhoea
Acromegaly
GH not essential in adults
high IGF1 (insulin like gf) supports dx
GH = diuretic, hence deficiency results in fluid retention, swelling, carpal tunnel (compression), HTN - can lead to stroke
doesn't always cause signs (spectrum)
GH normally suppressed by glucose load (if doesn't suppress then tumour - autonomous secretion)
DM (insulin resistance) common in acro - 25%
a/w increased risk of colonic polyps + maybe CRC (do colonoscopy)
Acromegalic CM, LVH, mitral regurg, cardiac death
gigantism is prepubertal (before long bones have fused)
abnormalities in acromegaly
recent acral growth (fingers + toes)
sweating
weakness
arthralgia
abnormal OGTT
dental malocclusion (misalignment when jaws close)
new skin tags
carpal tunnel
HTN > 150/95
male hypogonadism
hyperprolactinaemia (mixed tumours)
enlarged tongue/nose/jaw (causes teeth to space out)
these changes happen slowly - get photos from 10-15 yrs/ago
organomegaly
effects of acromegaly due to...
tumour expansion (headaches, visual defects, cranial N palsies)
GH hypersecretion
Hypopituitarism
Tx
surgery (experience NB)
radiotherapy
medical therapy
dopamine (inhibits PRL + GH release) agonists: cabergoline
somatostatin analogues: octreotide, lanreotide
GH R blocker: pegvisomant
replace pit hormones
tx co-morbidities (HTN etc)
Management
hormone replacement
hydrocortisone 1st (converted to cortisol in liver - most physiological)
thyroxine (if given 1st would make cortisol deficiency worse as increases cortisol clearance)
testosterone
surgical decompression
transcranial: rare, must open skull
transphenoidal: resect floor of pit fossa - access to tumour from below
post op radiotherapy (gamma) if tumour wasn't fully resectable
Prolactinomas
ED
v high PRL (normal = 50-350 mlU/l)
usually have good response to medical tx
surgery not needed
v sensitive to dopamine agonists (85-90% shrink)
small prolactinomas can cause a functional deficiency in gonadotrophs - infertility
Cortex zones
zona glomerulosa: just under capsule, makes aldosterone
zona fasciculata: largest, makes cortisol
zona reticularis: makes androgens
Primary aldosteronism (Conn's Syndrome)
inappropriate Na retention mediated via mineralocorticoid R
suppression of renin activity
HTN + hypokalaemic alkalosis
in 4-5% of HTN patients
Causes
aldosterone producing pit adenoma (originally what Conn described, autonomous secretion)
bilat idiopathic adrenal hyperplasia (exaggerated aldo response to Ang2)
primary hyperplasia, carc
glucocorticoid-suppressible hyperaldosteronism (hybrid cells)